When the program is run, this will show the user the message Enter your name: and will then save whatever the user inputs as the variable username. This can be very useful when writing a program to solve engineering type problems, as your program could ask the user to enter some parameters (such as mass, volume etc.) for your program to use.

Note:
In Python 2, input actually evaluates the input as python code. In the new version of Python, Python 3, input has the functionality of raw_input in Python 2. To replicate the functionality of input in Python 2, use eval(input).